The present invention relates generally to hydraulic mining tool apparatus and, more particularly, to an improved hydraulically mining tool apparatus for recovering minerals such as tar sands, from subterranean formations wherein a plurality of cutting jet nozzles adapted to hydraulically dislodge mineral particles from the formation are positioned to generate a hydraulic couple self-rotational force upon the mining tool and thereby reduce overall input power requirements for the apparatus.
The present invention further relates to and improves upon my previous filed U.S. patent applications Ser. No. 053,029 entitled "Downhole Pump Bottom Receptor," now issued U.S. Pat. No. 4,275,926; Ser. No. 121,712 entitled "Hydraulic Mining Tool Apparatus" now issued U.S. Pat. No. 4,296,970; and my copending patent applications Ser. No. 231,495 entitled "Apparatus and Method of Hydraulically Mining Subterranean Mineral Formations;" Ser. No. 232,439 now U.S. Pat. No. 4,415,206, entitled "Improved Drill String and Method of Hydraulically Mining Mineral Formations;" and Ser. No. 253,681, now U.S. Pat. No. 4,420,187, entitled "Stationary Drill String Hydraulic Mining Tool Apparatus.
Basically, the operation of such hydraulic mining tool apparatus is characterized by the use of a high velocity liquid stream which is discharged directly into the subterranean mineral formations to dislodge minerals from their surrounding mineral bed. The freed minerals form a resultant slurry with the discharged liquid stream which may be pumped by various means, upward to ground surface and subsequently processed by surface separation equipment. As the slurry is removed from the formation, a mining cavity or void is formed in the mineral bed which may extend to fifty to a hundred feet in diameter throughout the height of the mineral bed. The use of such hydraulic mining tool recovery operation is extremely suited for many mineral formations such as tar sands, which typically are located at vertical depths sufficiently below ground surface to prohibit strip mining recovery techniques while sufficiently close to ground surface to prohibit conventional mineral mining operations.
A constant cause of concern existing within the hydraulic mining tool technology has been the occurrence of a compaction or cave-in situation within the formation whereby the surrounding mineral bed catastrophically falls in and around the drill string of the mining tool during operation. As will be recognized, when such a compaction situation occurs, the weight force exerted upon the mining tool generates an extremely large torsional drag upon the mining tool. As such, the prior art mining tools have heretofore incorporated relatively large ground surface mechanisms to effectuate continuous rotation of the mining tool within the formation and have utilized high torsional strength connections along the length of the mining tool and drill string to insure against a twist-off condition resulting in the mining tool being irretrievably lost within the mineral formation. As will be recognized, the use of such relatively large rotating mechanisms has added substantially to the overall operating costs involved in recovering minerals from the formation while the purposeful engineering of high torsional strength connections along the mining tool and drill string has increased the initial capital investment costs of the mining tool apparatus.
In addition, the prior art hydraulic mining tool apparatus has typically utilized only a single hydraulic cutting jet nozzle to direct the hydraulic jet flow radially outward into the formation from the central axis of the tool. In such mining tools, the reactionary force generated by the discharge of the high velocity fluid has the potential to cause axial deflection of the tool and drill string during operation. Heretofore, the only attempts to alleviate these axial bending problems have been the intentional overdesign of the tool to be capable of resisting the same. As such, the costs of the prior art mining tools have been prohibitive.
A further deficiency of the prior art hydraulic mining tools has been their propensity of having their slurry inlet openings becoming obstructed by rocks and other formations debris during the mining process. When such rock debris accumulates adjacent the inlet openings, the amount of mined minerals slurry entering into the tool is substantially reduced, which therefore reduces the overall efficiency of the hydraulic mining process. Although this problem has been addresed to a limited extent in the prior art by providing the slurry inlet openings with screens adapted to prevent rock and the like from entering into the interior of the tool, the location of the screens and slurry inlets have typcially been proximate the lower end of the mining tool and have themselves been subject to becoming obstructed by large rock debris in the formation.
Thus, there exists an inherent need in the field for an improved hydraulic mining tool apparatus which reduces the power requirements of the rotating mechanism, minimizes cutting jet reactionary bending forces exerted upon the tool and permits the tool to be operated for prolonged duration without obstruction of the slurry inlet openings.